Hydraulic fluid circuit for vehicle having articulated sections

ABSTRACT

A hydraulic circuit having one or more pumps adjacent motor means in a machine with hydraulic motors which are supplied by the circuit being located in a relatively remote location from the pumps. A control valve is associated with each hydraulic motor and includes a return line in communication with a first hydraulic fluid tank. An assembly of one or more pumps for delivering fluid under pressure to the control valves is located adjacent the motor means and is driven by the motor means. A second hydraulic fluid tank is associated with the pump assembly, the second tank providing fluid to the pumps and being in communication with the first tank by a return conduit for delivering fluid from the first tank to the second tank. To prevent rupture of the first tank, a baffle is preferably arranged within that tank to assure a constant air pocket above the fluid.

United States Patent 1 Geselbracht et a1.

[451 July 23,1974

[ HYDRAULIC FLUID CIRCUIT FOR VEHICLE HAVING ARTICULATED SECTIONS Inventors:

Assignee:

Filed:

Appl. No.: 146,509

Thomas H. Geselbracht, Joliet; David S. Vinton, Morton, both of 111.

Caterpillar Tractor Co., Peoria, Ill.

May 24, 1971 Related US. Application Data Division of Ser. No. 834,776, June 19, 1969, Pat. No.

u.s. C1 180/53 R Int. Cl FlSb 15/18 Field of Search 180/66 R, 14 R, 51, 53 R,

References Cited UNITED STATES PATENTS Martin Beyerstedt Miller Lehmann Dorsey 180/14 R X 2/1966 Freedy 91/41 7/1970 Korotkin 180/66 R Primary Examiner-Kenneth 1-1. Betts Attorney, Agent, or FirmPhillips, Moore, Weissenberger, Lempio & Strabala [5 7 ABSTRACT A hydraulic circuit having one or more pumps adjacent motor means in a machine with hydraulic motors which are supplied by the circuit being located in a relatively remote location from the pumps.- A control valve is associated with each hydraulic motor and includes a return line in communication with a first hydraulic fluid tank. An assembly of one or more pumps for delivering fluid under pressure to the control valves is located adjacent the motor means and is driven by the motor means. A second hydraulic fluid tank is associated with the pump assembly, the second tank providing fluid to the pumps and being in communication with the first tank by a return conduit for delivering fluid from the first tank to the second tank.

To prevent rupture of the first tank, a baffle is preferably arranged within that tank to assure a constant air pocket above the fluid.

2 Claims, Drawing LIFT CYLINDERS HYDRAULIC FLUID CIRCUIT FOR VEHICLE HAVING ARTICULATED SEGTIONS v This application is a division of Ser. No. 834,776 filed June 19, 1969, now US. Pat. No.-3,604,20 5.

The present invention relates to a hydraulic circuit on a machine for circulating fluid between pumps driven by motor. means such asan engine and one or more control valves which are adjacent to, and regulate hydraulic motors supplied by the circuit. The present invention particularly contemplates the circuit for use inapplications where one or more hydraulic motors are relative remote from the motor means employed to drive one or more hydraulic pumps in the circuit.

The present invention is described below within an exemplary environment provided by an articulated material handling vehiclesuch as a bucket loader having :motor means for an engine on one articulated section and implements powered by hydraulic motors on the other articulated section. In such an environment, it is desirable to locate pumps for the circuit closely adjacent 38 engine from which they are driven. In the prior art, a hydraulic fluid tank or reservoir is commonlylocated adjacent the pumps with hydraulic fluid under pressure being communicated to the remote hydraulic particularly complicated on articulated vehicles of the type mentioned above since each .of the lines must cross the articulated axis of the vehicle and accordingly must include a swivel joint.

' The present invention substantially minimizes these problems and simplifies the hydraulic circuit through the use of two hydraulic fluid tanks. One of the tanks is associated with the hydraulic pump or pumps while the other tank is associated with one or more remotely located hydraulic motors and regulating control valves.

In such a hydraulic circuit, one of the tanks commonly has inlet means for'receiving fluid underpressure, for example, from the hydraulic motors supplied by the circuit. The tank also'has outlet means through which fluid exits the tank. Normally, the tank is maintained in a conditionwhere it is partly filled with fluid and has an air pocket above the fluid. Surges of fluid into the tank from the inlet means are normally prevented from rupturing the tank by the air pocket which tends to absorb any increasd pressures. However, during operation, air commonly tends to leak out of the tank, for example, through gasket material used to close the tank particularly under high-pressure .COIldI? tions caused by the fluid surges. If all of the air in the tank leaks into the atmosphereand the tank becomes filled with fluid, high pressures causedby subsequent fluid surges may tend to damage or rupture the tank. To solve this problem, the present invention contemplates the use of baffle means for maintaining an air pocket in the tank and preventing leakage of the air.

The manner in which the present invention fulfills these purposes is illustratedby the followingdescription wherein additional objects and advantages of the invention are also believed to be made apparent. The

invention is described below having reference to'the accompanying drawings. I

In the drawings: FIG. 1 is a schematic representation of the present I hydraulic circuit with various components of the circuit being shown in section; and

FIG. 2 is a side view in elevation of an articulated vehicle employing the present hydraulic circuit.

The present invention is described with particular referenceto an articulated vehicle of the'type illus trated in FIG. 2. However, it will be apparent that the hydraulic circuit may be employed in other vehicles or machines'which are not necessarily articulated but wherein motor means such as an engine for driving pumps of the circuit is located remotely from hydraulic .motors supplied by the circuit.

Momentarily referring to FIG. 2, an articulated vehicle 11 for which the present hydraulic circuit is particularly contemplated has two sections 12 and 13 joined together by an articulated. joint indicated at 14. For

' purposes of an example, the vehicle is illustrated as a bucket loader having a bucket 16 pivotallysupported by one or more lift arms such as that indicated at 17.

The position of the bucket is controlled by hydraulic tilt motors, one of which is indicated at 18, and hydrau liclift motors, one of which is indicated at 19. Each tilt motor is interconnected between the vehicle and the bucket by tilt linkage generally indicated at 21. Each hydraulic lift motor is pivotally interconnected between the vehicle and oneof the lift arms 17.

The tilt motors and lift'motorstogether with the bucket 16 are commonly supported by one of the articulated sections, for example that indicated at 13. An engine 22 for driving the vehicle is commonly located on the other articulated section 12.

When a hydraulic circuit of the type illustrated in greater detail in- FIG. 1 is adapted to such a vehicle, it

is desirable that the hydraulic pumps be located closely adjacent the engine 22 by which they are driven. Accordingly, a cluster arrangement 23 of hydraulic pumps is shown adjacent the engine 22 upon thev articulated section 12. f

The present invention is believed to substantially simplify construction of a hydraulic circuit for properly interconnecting'the pump cluster 23 with the hydraulic motors such as those indicated at 18 and 19. A hydraucated at 13' and generally including'those components to the right of the section line 31 in FIG. 1 are arranged upon the other articulated section 13 which also supports the bucket implement 16. As illustrated in FIG.

. l, the pump cluster 23 includes two double sectioned pumps 32 and 33. Fluid under pressure from the pumps 32 and 33 is selectively directed to the hydraulic motors l8 and 19 bycontrol valves 34 and 36 respectively. The circuit also includes a first hydraulic fluid tank or reservoir 37 which receives fluid from the control valves 34, 36 and a second hydraulic fluid tank 38 from which fluid is drawn into the pumps 32, 33 by an inlet conduit 39.

To describe various componentsof the circuit in greater detail, the control valves are of a type suitable for immerging in hydraulic fluid. Accordingly, the control valves 34, 36 are shown within the first tank 37. The tank 37 has a generally low, wide profile so that the control valves may be arranged in generally horizontally relation adjacent the bottom of the tank.

' Fluid under pressure from the pump 32 is combined in a manifold 41 from where it passes into an outlet conduit 42. The conduit 42 is also-in communication with the control valve 34. The valve 34includes a spool, generally indicated at 43, which may be positioned to direct fluid from theconduit 42 into either end of the hydraulic motor 18 by respective conduits 44 and 46. The spool 43 may also be positioned so that fluid from the conduit 42 passes directly into a fluid return line 47 which communicates the control valve 34 with the first tank 37. Whenthe control valve is adjusted to direct fluid into either end of the motor 18,

exhaust fluid from the other end of the motor 18 is also,

delivered by the control valve into the return conduit 47.

The other pump 33 is similarly in communication with the control valve 36 by a manifold 51 and a highpressure outlet conduit 52. The control valve 36 includes a control spool generally indicated at 53. The control valve 36 is similarly in .communication with both ends of the hydraulic motor 19 through respective conduits 54 and56 and with the first tank 37 by means of the same fluidreturn line 47. r

The first tank 37 is in communication with the second tank 38 by means of a return conduit indicated at 61. The return conduit 61 is in communication with the first tank 37 by means of a stand pipe 62 which normally establishes the fluid level inthe firsttank 37. A baffle assembly 63 is arranged at one end of the return conduit 61 to prevent aeration of the fluid entering the second tank 38. A similar baffle assembly 64 is mounted on the fluid return 47 in communication with the first tank 37. Under normal operating conditions, both tanks 37, 38 are partly filled with hydraulic fluid to form air pockets in the tops of the tanks. Fluid under pressure is delivered into the first tank 37 through the tank itself.

To commence operation of the present hydraulic cirtop of the first tank 37 during operation of the system.

This air pocket provides a cushion-for pressure surges within'the tank and thereby prevents damage to the cuit, hydraulic fluid is firstintroduced into the first tank 37 until it reaches the top of stand pipe 62. The second tank 38 is then filled with fluid to a somewhat lower level which may be determined for example by a sight fluid return 47 which tends to increase pressure in its air pocket generally indicated at 66. When the fluid level in the first tank 37 is above the top of'stand pipe 62, the increased pressure causes excess fluid to flow into the second tank 38. Thus, pressure within the first tank 37 will normally be slightly higher than air pressure in the second tank 38 by the differential pressure drop required to transmit fluid through the return conduit 61. The two tanks 37, 38 are relatively positioned so that the normal fluid level in the first tank 37 is somewhat higher than the fluid level in the second tank Since all return fluid from the control valves 34, 36 is delivered to the first tank 37, surges of fluid, for example exhausted; from the hydraulic motors l8.and'19 may substantially increase the pressure in the first tank. These pressure surges tend to cause air within the tank 37 to' leak to the atmosphere, particularly across'the gasket material'67 which seals the cover 68 in place atop the first tank 37. If this leakage is permitted to continue, the first tank 37 could become entirely filled gauge 73. The pumps 32, 33 are then momentarily operated so that all of the conduits and other components of the circuit are filled with fluid. The pumps are then shut down and the second tank 38 is again filled to a level somewhat lower than the fluid level determined by the stand pipe 62 in the first tank 37.

The fluid may be added to the first and second tanks by means of filler caps indicated at 74 and 76 respectively. To completely prevent leakage of air from the region 72 past the filler cap 74, a cylindrical pipe 77 supporting the cap' 74 is hermetically secured to the cover 68 and extends downwardly at least as far as the baffle7l. I

What is claimed is:

1. A hydraulic circuit for a vehicle having an engine and a hydraulic motor remotely located from the engine of the vehicle, the vehicle having two sections joined in articulated relation, the engine being on one articulatedsection and the hydraulic motor being on the other articulated section, comprising at least one hydraulic pump associated in driven relation with the engine,

a control valve associated withthe hydralic motor,

said control valve being in communication with a fluid outlet conduit of said pump, said control valve being selectively operable to .deliver fluid under pressure for operating the hydraulic motor,

a first hydraulic fluid tank associated with said control valve, said first tank being in communication with a fluid return from said valve,

a second hydraulic fluid tank associated with 'said pump, said second tank being in communication with an inlet conduit to said pump,

said pump and second tank being located on the one articulated section, said valve and first tank being located on the other articulated section, and' a return conduit providing substantially free communication between said first and second tanks for delivering hydraulic fluid from said first tank to said second tank, said retu'mconduit including a stand pipe in said first tank for establishing a normal fluid 'level thereinav 2. A hydraulic circuit for a vehicle having motor means, at least one implement and a hydraulic motor for operating the implement being'remotely located from the motor means, comprising a hydraulic pump associated with and coupled in driven relation to the motor means,

a return conduit substantially freely communicating said two tanks for delivering fluid from said first tank to said second tank, said return conduit including a stand pipe in said first tank for establishing a normal fluid level therein, and

wherein the vehicle is comprised of two articulated sections, the motor means, said pump and second tank being located on one articulated section, the

, implement, said control valve and first tank being located on the other articulated section. 

1. A hydraulic circuit for a vehicle having an engine and a hydraulic motor remotely located from the engine of the vehicle, the vehicle having two sections joined in articulated relation, the engine being on one articulated section and the hydraulic motor being on the other articulated section, comprising at least one hydraulic pump associated in driven relation with the engine, a control valve associated with the hydralic motor, said control valve being in communication with a fluid outlet conduit of said pump, said control valve being selectively operable to deliver fluid under pressure for operating the hydraulic motor, a first hydraulic fluid tank associated with said control valve, said first tank being in communication with a fluid return from said valve, a second hydraulic fluid tank associated with said pump, said second tank being in communication with an inlet conduit to said pump, said pump and second tank being located on the one articulated section, said valve and first tank being located on the other articulated section, and a return conduit providing substantially free communication between said first and second tanks for delivering hydraulic fluid from said first tank to said second tank, said return conduit including a stand pipe in said first tank for establishing a normal fluid level therein.
 2. A hydraulic circuit for a vehicle having motor means, at least one implement and a hydraulic motor for operating the implement being remotely located from the motor means, comprising a hydraulic pump associated with and coupled in driven relation to the motor means, a control valve hydraulically associated with the hydraulic motor, said control valve being in communication with said pump by a high pressure fluid conduit, a first hydraulic fluid tank associated with said control valve, said first tank being in communication with a fluid return line from said valve, a second hydraulic fluid tank associated with said pump, said second tank being in communication with an inlet conduit for delivering hydraulic fluid to said pump, a return conduit substantially freely communicating said two tanks for delivering fluid from said first tank to said second tank, said return conduit including a stand pipe in said first tank for establishing a normal fluid level therein, and wherein the vehicle is coMprised of two articulated sections, the motor means, said pump and second tank being located on one articulated section, the implement, said control valve and first tank being located on the other articulated section. 